The 42-year-old pop star "knew that Casper really wanted a truck, and Casper was VERY excited about the generous gift," a source told the magazine.Lopez also Tweeted: "Beau has a birthday we're so glad we hope it's the happiest Birthday Beau ever has!' #singingtweet. HAPPY BIRTHDAY BEAR!!!"
The two have been dating since last November.
Watch their steamy new music video to J.Lo's single, "Dance Again."